Diamond And Wide-bandgap Materials Lead The Technological Innovation in Electric Vehicles

The rapid development of electric vehicles (EVs) has imposed higher demands on power electronic converters: efficiency, compactness, and reliability. Traditional silicon (Si)-based semiconductors have approached their theoretical limits, while wide bandgap (WBG) and ultra-wide bandgap (UWBG) semiconductor materials are emerging as next-generation solutions.

 

This article primarily focuses on the latest advancements of wide-bandgap semiconductor devices in electric vehicle power converters, with an in-depth analysis of the characteristics, manufacturing challenges, and device performance of silicon carbide (SiC), gallium nitride (GaN), as well as emerging materials such as diamond and gallium oxide (Ga₂O₃). It also examines the applicability of these materials in critical EV systems like traction inverters, onboard chargers (OBCs), and DC-DC converters, while discussing their technical maturity, research gaps, and future trends to explore the potential of wide-bandgap technology in electric mobility.

Material characteristics of wide-bandgap semiconductors

The core of energy conversion in electric vehicles is the power electronic converter, whose performance heavily relies on semiconductor switching devices. Silicon, with its narrow bandgap (1.12 eV), is constrained in high voltage, high temperature, and high-frequency operation, making it increasingly difficult to meet the demands of next-generation high-density, high-efficiency EV power systems.

 

Wide bandgap semiconductors typically have bandgaps exceeding 2 eV, featuring higher breakdown electric fields, lower on-state resistance, and excellent thermal conductivity.

 

The primary materials include:

 

Silicon carbide (SiC)

The most mature wide-bandgap technology features a bandgap of 3.26 eV, a breakdown electric field of 3–5 MV/cm, and a thermal conductivity of 3.0–4.9 W/cm·K (approximately three times that of silicon). 4H-SiC is the mainstream polytype for power devices, with 150 mm wafers already in mass production and 200 mm wafers nearing commercialization. SiC MOSFETs excel in high-voltage systems above 800 V, significantly reducing conduction and switching losses, improving inverter efficiency by several percentage points, and extending vehicle range. The primary challenge lies in the high interface trap density of SiC/SiO₂, but techniques like nitrogen passivation have greatly enhanced reliability. In low-temperature (cryogenic) environments, the on-resistance and switching losses of high-voltage SiC devices increase significantly, making them unsuitable for extreme low-temperature applications.

 

Gallium Nitride (GaN)

With a bandgap of 3.4 eV, the two-dimensional electron gas (2DEG) formed by AlGaN/GaN heterojunction has an electron mobility of up to 2000 cm ²/V · s, extremely low on resistance, and a switching frequency of up to MHz. GaN has obvious advantages in high-frequency and medium voltage (<650 V) applications, which can significantly reduce the volume and weight of passive components in car chargers and DC-DC converters. At low temperatures, the performance of GaN is actually improved, with reduced on resistance and faster switching speed, making it very suitable for extreme environments. However, GaN lacks inexpensive intrinsic substrates and is often grown epitaxially on silicon, resulting in lattice mismatch and defect issues; The manufacturing of enhanced (normally off) devices is also more complex.

 

diamond

Ultra wide bandgap (5.47 eV), theoretical breakdown electric field of 20 MV/cm, thermal conductivity of 22 W/cm · K (more than 5 times that of SiC), theoretical performance far exceeds other materials, and nearly 10 kV Schottky diodes and extremely high Baliga merit values have been reported. However, n-type doping is difficult and the substrate cost is high. The commercialization of diamond power devices may take time, but their potential in ultra-high voltage and high temperature applications is unparalleled.

 

β - Gallium oxide (Ga ₂ O ∝)

With a bandgap of 4.5-4.9 eV and a breakdown electric field of 8 MV/cm, large-sized single crystal substrates can be grown by melt method (such as Czochralski) with low manufacturing cost potential. The main drawback is extremely low thermal conductivity (0.1-0.3 W/cm · K), requiring advanced cooling solutions; P-type doping is difficult, and most devices are unipolar. Suitable for future ultra-high voltage applications.

 

Comparison of material properties and suitability for EV applications

The characteristics of different materials determine their optimal application scenarios in different subsystems of EV:

• Traction inverter (high voltage, 800 V+system)
• SiC is optimal. High voltage capability, high thermal conductivity, and simple cooling system have widely replaced silicon IGBTs, improving efficiency and extending battery life.
• Car charger (OBC) and DC-DC converter
• GaN is the best. High frequency operation significantly reduces the volume of passive components, achieving a power density of 3-5 kW/L or higher, reducing vehicle weight and lowering costs.
• Wireless Charging (WPT)
• GaN's high-frequency characteristics naturally adapt to resonant converters ranging from hundreds of kHz to MHz.
• Ultra high voltage future scenarios (such as heavy-duty trucks, power grid interfaces)
• Diamond and Ga ₂ O3 have the greatest potential to simplify topology and reduce series connected devices.
• In terms of low-temperature performance, GaN and silicon exhibit excellent performance, while high-voltage SiC performance decreases, and careful selection should be made according to the application scenario.

 

Potential Application and Engineering Prospects of Diamond in Efficient EV Power Converter

Diamond is regarded as the next generation material surpassing SiC/GaN due to its ultra wide bandgap and extremely high thermal conductivity. The main challenges are the difficulty of n-type doping (phosphorus/nitrogen deep level, low room temperature activation rate) and the high cost of large-sized single crystal substrates, but recent progress has been significant.

 

Japan's Power Diamond Systems (PDS) showcases real-time operation diamond power MOSFET prototypes at SEMICON Japan 2025, with plans to ship samples for EV inverters and satellites in the 2026 fiscal year.

French Diamfab advances 4-inch synthetic diamond wafers to build a European diamond ecosystem, targeting power electronics, with an expected industrial prototype by 2026.

The Diamond Foundry Perseus prototype (2023) has a demonstration volume six times smaller and higher power density than the Tesla Model 3 inverter.

Potential for EV system integration

The high breakdown field strength of diamond enables it to directly interface with high-voltage systems, simplifying the topology of power converters and reducing the number of required devices. In addition, the ultra-high thermal conductivity of diamond simplifies the cooling system, achieving higher power density (several times higher than current SiC devices). Diamond has broad potential applications in ultra-high voltage traction inverters, ultra compact car chargers, and high-temperature tolerant systems.

 

Thermal Management and Reliability

The ultra-high thermal conductivity of diamond makes it particularly suitable for high-power EV systems, enabling efficient heat dissipation without the need for complex cooling. Diamond performs better than SiC and GaN in high temperature and radiation environments.

 

Conclusions and Prospects

Wide bandgap semiconductors are reshaping the power electronics landscape of electric vehicles. SiC dominates high-voltage traction inverters, GaN leads high-frequency and high-density applications, while diamond and Ga ₂ O3 represent the future direction of ultra-high voltage and extreme environments. The selection of materials should comprehensively consider voltage level, switching frequency, thermal management, and cost.

 

The current main challenges include: SiC interface optimization, GaN high-voltage reliability, and doping and substrate issues of diamond/Ga ₂ O3. With the maturity of manufacturing processes, wide bandgap devices will further enhance the efficiency, range, and charging speed of electric vehicles, while promoting extensive innovation in power electronics in the fields of power grid, industry, and aviation.